Method and apparatus for exchanging variable length frames by fixed length cell handling exchange

• US 5,610,918 A
• Filed: 01/31/1994
• Issued: 03/11/1997
• Est. Priority Date: 06/08/1993
• Status: Expired due to Term

• Current Assignee: Fujitsu Limited
• Original Assignee: Fujitsu Limited
• Inventors: Watanabe, Yoshihiro, Kamo, Toshiyuki
• Primary Examiner(s): Olms, Douglas W.
• Assistant Examiner(s): TON, DANG T
• Application Number:
  US08/189,961
• Time in Patent Office: 1,135 Days
• Field of Search: 370/82, 370/60, 370/94.1, 370/83, 370/84, 370/110.1, 370/60.1, 370/95.1, 370/85.7, 370/95.3, 370/97
• US Class Current: 370/395.5
• CPC Class Codes: H04J 3/1647 Subrate or multislot multiplexing
• CPC Class Codes: H04L 12/2854 Wide area networks, e.g. public data networks
• CPC Class Codes: H04Q 11/0478 Provisions for broadband connections

Abstract

The invention provides a variable length frame exchanging method adapted to a fixed length cell handling exchange into which a terminal for use with a data communication method by a variable length frame is accommodated, a variable length frame exchanging interface apparatus and a call acceptance determination system, which are improved in that a variable length frame can be exchanged at a high speed in a fixed length cell handling exchange network and a terminal can be connected to and accommodated into the exchange in the same conditions as an existing service. The terminal is connected to the exchange by way of a subscriber line including a plurality of channels. A variable length frame from the terminal is disassembled into fixed length cells, and a use channel number or numbers and a DLCI of the subscriber line are converted into a VPI and a VCI. The VPI and the VCI are added to each of the fixed length cells, respectively, and the resulted fixed length cells are inputted to the exchange so that the frame is exchanged by the exchange.

Claims

1. A variable length frame exchanging method by a fixed length cell handling exchange which handles fixed length cells each including a first logic channel information, a logic path information and a data section and to which a terminal adapted for a data communication using a variable length frame including a second logic channel information is connected by a transmission line having at least one channel, the method comprising the steps of:

disassembling the variable length frame transmitted from said terminal into fixed length cells;

translating the second logic channel information in the variable length frame into the first logic channel information and the logic path information for the fixed length cells; and

providing the first logic channel information and the logic path information obtained in said translating step for the fixed length cells obtained in said disassembling step and inputting the fixed length cells with the first logic channel information and the logic path information to said exchange.

2. A variable length frame exchanging method by a fixed length cell handling exchange which handles fixed length cells each including a first logic channel information, a logic path information and a data section and to which a terminal adapted for a data communication using a variable length frame including a second logic channel information is connected by a transmission line having at least one channel, the method comprising the steps of:

producing, when fixed length cells designating said terminal as a destination of transmission are outputted from said exchange to said transmission line, a frame from the fixed length cells;

translating the first logic channel information and the logic path information for the fixed length cells into the second logic channel information in the variable length frame; and

providing said frame obtained in said producing step with the second logic information obtained in said translating step and inputting said frame with the second logic channel information in the variable length frame obtained in said translating step to said terminal.

3. A variable length frame exchanging method by a fixed length cell handling exchange which handles fixed length cells each including a first logic channel information and a data section and to which a terminal adapted for a data communication using a variable length frame including a second logic channel information is connected by a transmission line having at least one channel, the method comprising the steps of:

disassembling the variable length frame transmitted from said terminal into fixed length cells;

converting the second logic channel information in the variable length frame into the first logic channel information for the fixed length cells;

providing the first logic channel information obtained in said converting step for the fixed length cells obtained in said disassembling step and inputting the fixed length cells with the first logic channel information to said exchange;

producing, when fixed length cells designating said terminal as a destination of transmission are outputted from said exchange to said transmission line, a frame from the fixed length cells;

converting the first logic channel information for the fixed length cells into the second logic channel information in the variable length frame; and

providing said frame obtained in said producing step and inputting said frame with the second logic channel information in the variable length frame obtained in said step of converting the first logic channel information, to said terminal.

4. A variable length frame exchanging method by a fixed length cell handling exchange as claimed in claim 3, wherein the first logic channel information for the fixed length cells includes virtual path identifier information and virtual channel identifier information, and the second logic channel information includes a channel number or numbers of said transmission line which have been used to transmit the frame from said terminal and data link connection identifier information and wherein a first corresponding relationship between the virtual path identifier information and a channel number or numbers of said transmission line used between said terminal and said exchange and a second corresponding relationship between the virtual channel identifier information and a data link connection identifier to be provided to a frame are registered in advance, and wherein,

when a frame is to be transmitted from said terminal to said exchange, a channel number or numbers of said transmission line which have been used to transmit the frame from said terminal of the second logic channel information are converted into virtual path identifier information of the first logic channel information in accordance with the first corresponding relationship and data link connection identifier information to be provided to the frame of the second logic channel information is converted into virtual channel identifier information of the first logic channel information in accordance with the second corresponding relationship, but when fixed length cells designating said terminal as a destination of transmission are outputted from said exchange to said subscriber line, virtual channel identifier information of the first logic channel information to be provided for the fixed length cells is converted into data link connection identifier information of the second logic channel information in accordance with the second corresponding relationship and virtual path identifier information of the first logic channel information to be provided for the fixed length cells is converted into a channel number or numbers of said transmission line which are available upon transmission of the frame to said terminal of the second logic channel information in accordance with the first corresponding relationship.

5. A variable length frame exchanging interface apparatus which is interposed in a transmission line having at least one channel for interconnecting an exchange which handles fixed length cells each including a first logic channel information and a data section and a terminal adapted for a data communication using a variable length frame including a second logic channel information, and which performs conversion processing between the fixed length cells for said exchange and a variable length frame for said terminal, the apparatus comprising:

frame production means for producing a frame based on data transmitted thereto from said terminal by a plurality of channels of said transmission line;

wherein the first logic channel information includes virtual path identifier information and virtual channel identifier information and the second logic channel information includes a channel number or numbers of said transmission line which have been used to transmit the frame from said terminal and data link connection identifier information,

first conversion means for converting a channel number or numbers of said transmission line which have been used to transmit the frame from said terminal of the second logic channel information in the variable length into virtual path identifier information of the first logic channel information for the fixed length cells;

second conversion means for converting data link connection identifier information of the second logic channel information to be added to the frame into the virtual channel identifier information of the first logic channel information for the fixed length cells; and

disassembling means for disassembling the frame into fixed length cells to which the virtual path identifier information obtained by conversion of said channel number or numbers into the virtual path identifier information in said first conversion means and the virtual channel identifier information obtained by conversion of said data link connection identifier information into the virtual channel identifier information in said second conversion means are added and sending out the fixed length cells with the added virtual path identifier information and the virtual channel identifier information to said exchange.

6. A variable length frame exchanging interface apparatus as claimed in claim 5, wherein said first conversion means includes first storage means for storing in advance a first corresponding relationship between a channel number or numbers of said transmission line which are used between said terminal and said exchange and the virtual path identifier information, and said second conversion means includes second storage means for storing in advance a second corresponding relationship between a data link connection identifier to be added to the frame and the virtual channel identifier information.

7. A variable length frame exchanging interface apparatus which is interposed in a transmission line having at least one channel for interconnecting an exchange which handles fixed length cells each including a first logic channel information and a data section and a terminal adapted for a data communication using a variable length frame including a second logic channel information, and which performs conversion processing between fixed length cells for said exchange and a variable length frame for said terminal, the apparatus comprising:

frame assembling means for assembling a frame based on fixed length cells from said exchange designating said terminal as a destination of transmission;

wherein the first logic channel information includes virtual path identifier information and virtual channel identifier information and the second logic channel information includes a channel number or numbers of said transmission line which have been used to transmit the frame from said terminal and data link connection identifier information,

first conversion means for converting the virtual channel identifier information of the first logic channel information for the fixed length cells into the data link connection identifier information of the second logic channel information to be added to the frame;

second conversion means for converting the virtual path identifier information of the first logic channel information for the fixed length cells into a channel number or numbers of said transmission line which are available upon transmission to said terminal of the second logic information; and

frame disassembling means for disassembling and transmitting the frame, to which the data link connection identifier information obtained by conversion of said virtual channel identifier information into the data link connection identifier information in said first conversion means is added, by a channel or channels corresponding to the channel number or numbers of said transmission line obtained by conversion of said virtual path identifier information into the channel number or numbers in said second conversion means, to said terminal.

8. A variable length frame exchanging interface apparatus as claimed in claim 7, wherein said second conversion means includes first storage means for storing in advance a first corresponding relationship between the virtual path identifier information and a channel number or numbers of said subscriber line which are used between said terminal and said exchange, and said first conversion means includes second storage means for storing in advance a second corresponding relationship between the virtual channel identifier information and a data link connection identifier to be added to a frame.

9. A variable length frame exchanging interface apparatus which is interposed in a transmission line having at least one channel for interconnecting an exchange which handles fixed length cells each including a first logic channel information and a data section and a terminal adapted for a data communication using a variable length frame including a second logic channel information, and which performs conversion processing between fixed length cells for said exchange and a variable length frame for said terminal, the apparatus comprising:

frame production means for producing a frame based on data transmitted thereto from said terminal by a plurality of channels of said transmission line;

wherein the first logic channel information includes virtual path identifier information and virtual channel identifier information and the second logic channel information includes a channel number or numbers of said transmission line which have been used to transmit the frame from said terminal and data link connection identifier information,

first conversion means for converting a channel number or numbers of said subscriber line which have been used to transmit the frame from said terminal of the second logic channel information into the virtual path identifier information of the first logic channel information for the fixed length cells;

second conversion means for converting the data link connection identifier information of the second logic channel information to be added to the frame into the virtual channel identifier information of the first logic channel information for the fixed length cells;

first frame disassembling means for disassembling the frame into fixed length cells to which the virtual path identifier information obtained by conversion of said channel number or numbers into the virtual path identifier information in said first conversion means and the virtual channel identifier information obtained by conversion of said data link connection identifier information into the virtual channel identifier information in said second conversion means are added and sending out the fixed length cells with the added virtual path identifier information and the virtual channel identifier information to said exchange;

frame assembling means for assembling a frame based on the fixed length cells from said exchange designating said terminal as a destination of transmission;

third conversion means for converting the virtual channel identifier information of the first logic channel information for the fixed length cells into the data link connection identifier information of the second logic channel information to be added to the frame;

fourth conversion means for converting the virtual path identifier information of the first logic channel information for the fixed length cells into a channel number or numbers of said transmission line which are available upon transmission to said terminal of the second logic channel information; and

second frame disassembling means for disassembling and transmitting the frame, to which the data link connection identifier information obtained by conversion of said virtual channel identifier information into the data link connection identifier information in said third conversion means is added, by a channel or channels corresponding to the channel number or numbers of said transmission line obtained by conversion of said virtual path identifier information into the channel number or numbers of said transmission line in said fourth conversion means, to said terminal.

10. A variable length frame exchanging interface apparatus as claimed in claim 9, wherein said first conversion means and said fourth conversion means commonly include first storage means for storing in advance a first corresponding relationship between the virtual path identifier information and the channel number or numbers of said transmission line which are used between said terminal and said exchange;

and said second conversion means and said third conversion means commonly include second storage means for storing in advance a second corresponding relationship between the virtual channel identifier information and the data link connection identifier information to be added to a frame.

11. A call acceptance determination system for a fixed length cell handling exchange including one or more first terminals adapted for a data communication method using fixed length cells each including a first logic channel information and a data section and one or more second terminals adapted for a data communication using a variable length frame including a second logic channel information wherein said terminals are connected to said exchange by respective transmission lines, the system comprising:

said exchange having a resource divided into a first terminal resource and a second terminal resource separate from each other;

first terminal resource control means for controlling the first terminal resource and second terminal resource control means for controlling the second terminal resource;

said first terminal resource control means including fixed length cell call acceptance determination means for determining whether or not a fixed length cell call from one of said first terminals should be accepted when the first terminal tries to use the first terminal resource;

said second terminal resource control means including frame call acceptance determination means for determining whether or not a frame call from one of said second terminals should be accepted when the second terminal tries to use the second terminal resource.

12. A call acceptance determination system for a fixed length cell handling exchange as claimed in claim 11, wherein said frame call acceptance determination means includes:

virtual band calculation means for multiplying a use requested band requested to set from one of said second terminals by a predetermined multiplexing rate to calculate a use virtual band which is controlled by the network;

subscriber line free band detection means for detecting a free band for said transmission lines for said second terminal;

outgoing line free band detection means for detecting a free band for the outgoing lines for said second terminal;

first comparison means for comparing the use requested band calculated by said virtual band calculation means and the free band detected by said subscriber line free band detection means with each other;

second comparison means for comparing the use requested band calculated by said virtual band calculation means and the free band detected by said outgoing line free band detection means with each other; and

call acceptance means for accepting a frame call from one of said second terminals when the comparison by said first comparison means proves that the use virtual band is smaller than the free band of said subscriber lines for said second terminals and the comparison by said second comparison means proves that the use virtual band is smaller than the free band for the outgoing lines for said second terminal.

13. A call acceptance determination system for a fixed length cell handling exchange as claimed in claim 12, wherein a use requested band requested to set from one of said second terminals is added as band information to a frame call from the second terminal and is transmitted to said virtual band calculation means of said frame call acceptance determination means together with the frame call.

14. A call acceptance determination system for a fixed length cell handling exchange as claimed in claim 11, wherein said frame call acceptance determination means includes:

virtual band setting means for setting, when setting of a frame call is requested from one of said second terminals, a physical maximum speed of the second terminal as a use virtual band for the frame call;

band assurance determination means for determining whether or not a band has been assured already for a same sending subscriber as the second terminal;

free band detection means for detecting a free band for said lines for said second terminal;

comparison means for comparing the use virtual band set by said virtual band setting means and the free band detected by said free band detection means with each other; and

call acceptance means for accepting, when said band assurance determination means determines that a band has been assured already for the same sending subscriber as the second terminal, the frame call from the second terminal unconditionally and for assuring, when said band assurance determination means determines that no band has been assured as yet for the same sending subscriber as the second terminal and the comparison by said comparison means proves that the use virtual band is smaller than the free band for said lines for said second terminal, the use virtual band and accepting the frame call from the second terminal.

22. A call acceptance determination system for a fixed length cell handling exchange as claimed in claim 14, wherein the predetermined multiplexing rate by which a use requested band is multiplied by said virtual band calculation means has two values set in advance including a first multiplexing rate for a use requested band requested to set from one of said first terminals and a second multiplexing rate for another use requested band requested to set from one of said second terminals.

28. A call acceptance determination system for a fixed length cell handling exchange as claimed in claim 22, wherein a use requested band requested to set from one of said second terminals is added as band information to a frame call from the second terminal and then transferred to said virtual band calculation means of said common resource call acceptance determination means together with the frame call.

15. A call acceptance determination system for a fixed length cell handling exchange accommodating one or more first terminals adapted for a data communication using fixed length cells each including a first logic channel information and a data section and one or more second terminals adapted for a data communication using a variable length frame including a second logic channel information wherein said terminals are connected to the exchange by respective transmission lines, the system comprising:

first terminal subscriber resource control means for controlling a first terminal subscriber access resource for a case wherein a fixed length cell call from one of said first terminals is inputted to said exchange;

second terminal subscriber resource control means for controlling a second terminal subscriber access resource for a case wherein a frame call from one of said second terminals is inputted to said exchange; and

network resource control means for controlling a network common resource for a case wherein a fixed length cell call from one of said first terminals or a frame call from one of said second terminals is inputted to said exchange;

said first terminal subscriber resource control means including fixed length cell call acceptance determination means for determining whether or not a fixed length cell call from one of said first terminals should be accepted when the first terminal tries to use the first terminal subscriber access resource;

said second terminal resource control means including frame call acceptance determination means for determining whether or not a frame call from one of said second terminals should be accepted when the second terminal tries to use the second terminal subscriber access resource;

said network resource control means including common resource call acceptance determination means for determining whether or not a fixed length cell call from one of said first terminals or a frame call from one of said second terminals should be accepted when the first terminal or the second terminal tries to use the network common resource.

16. A call acceptance determination system for a fixed length cell handling exchange as claimed in claim 15, wherein said frame call acceptance determination means includes:

virtual band calculation means for multiplying a use requested band requested to set from one of said second terminals by a predetermined multiplexing rate to calculate a use virtual band which is controlled by the network;

incoming side subscriber line free band detection means for detecting a free band for the incoming side transmission lines for said second terminal;

outgoing side subscriber line free band detection means for detecting a free band for the outgoing side transmission lines for said second terminal;

first comparison means for comparing the use virtual band calculated by said virtual band calculation means and the free band detected by said incoming side subscriber line free band detection means with each other;

second comparison means for comparing the use virtual band calculated by said virtual band calculation means and the free band detected by said outgoing side subscriber line free band detection means with each other; and

call acceptance means for accepting a frame call from one of said second terminals when the comparison by said first comparison means proves that the use virtual band is smaller than the free band for said incoming side subscriber lines for said second terminal and the comparison by said second comparison means proves that the use virtual band is smaller than the free band for said outgoing side subscriber lines for said second terminal.

17. A call acceptance determination system for a fixed length cell handling exchange as claimed in claim 16, wherein a use requested band requested to set from one of said second terminals is added as band information to a frame call from the second terminal and then transferred to said virtual band calculation means of said frame call acceptance determination means together with the frame call.

18. A call acceptance determination system for a fixed length cell handling exchange as claimed in claim 15, wherein said common resource call acceptance determination means includes:

virtual band calculation means for multiplying a use requested band requested to set from one of said first terminals or from one of said second terminals by a predetermined multiplexing rate to calculate a use virtual band which is controlled by the network;

common resource free band detection means for detecting a free band on the network common resource of said exchange;

comparison means for comparing the use virtual band calculated by said virtual band calculation means and the free band detected by said common resource free band detection means with each other; and

call acceptance means for accepting a fixed length cell call from one of said first terminals or a frame call from one of said second terminals when the comparison by said comparison means proves that the use virtual band is smaller than the free band on the network common resource.

19. A call acceptance determination system for a fixed length cell handling exchange as claimed in claim 16, wherein said common resource call acceptance determination means includes:

virtual band calculation means for multiplying a use requested band requested to set from one of said first terminals or from one of said second terminals by a predetermined multiplexing rate to calculate a use virtual band which is controlled by the network;

common resource free band detection means for detecting a free band on the network common resource of said exchange;

comparison means for comparing the use virtual band calculated by said virtual band calculation means and the free band detected by said common resource free band detection means with each other; and

call acceptance means for accepting a fixed length cell call from one of said first terminals or a frame call from one of said second terminals when the comparison by said comparison means proves that the use virtual band is smaller than the free band on the network common resource.

20. A call acceptance determination system for a fixed length cell handling exchange as claimed in claim 17, wherein said common resource call acceptance determination means includes:

virtual band calculation means for multiplying a use requested band requested to set from one of said first terminals or from one of said second terminals by a predetermined multiplexing rate to calculate a use virtual band which is controlled by the network;

common resource free band detection means for detecting a free band on the network common resource of said exchange;

comparison means for comparing the use virtual band calculated by said virtual band calculation means and the free band detected by said common resource free band detection means with each other; and

call acceptance means for accepting a fixed length cell call from one of said first terminals or a frame call from one of said second terminals when the comparison by said comparison means proves that the use virtual band is smaller than the free band on the network common resource.

21. A call acceptance determination system for a fixed length cell handling exchange as claimed in claim 18, wherein the predetermined multiplexing rate by which a use requested band is multiplied by said virtual band calculation means has two values set in advance including a first multiplexing rate for a use requested band requested to set from one of said first terminals and a second multiplexing rate for another use requested band requested to set from one of said second terminals.

23. A call acceptance determination system for a fixed length cell handling exchange as claimed in claim 20, wherein the predetermined multiplexing rate by which a use requested band is multiplied by said virtual band calculation means has two values set in advance including a first multiplexing rate for a use requested band requested to set from one of said first terminals and a second multiplexing rate for another use requested band requested to set from one of said second terminals.

24. A call acceptance determination system for a fixed length cell handling exchange as claimed in claim 18, wherein a use requested band requested to set from one of said second terminals is added as band information to a frame call from the second terminal and then transferred to said virtual band calculation means of said common resource call acceptance determination means together with the frame call.

25. A call acceptance determination system for a fixed length cell handling exchange as claimed in claim 19, wherein a use requested band requested to set from one of said second terminals is added as band information to a frame call from the second terminal and then transferred to said virtual band calculation means of said common resource call acceptance determination means together with the frame call.

26. A call acceptance determination system for a fixed length cell handling exchange as claimed in claim 20, wherein a use requested band requested to set from one of said second terminals is added as band information to a frame call from the second terminal and then transferred to said virtual band calculation means of said common resource call acceptance determination means together with the frame call.

27. A call acceptance determination system for a fixed length cell handling exchange as claimed in claim 21, wherein a use requested band requested to set from one of said second terminals is added as band information to a frame call from the second terminal and then transferred to said virtual band calculation means of said common resource call acceptance determination means together with the frame call.

29. A call acceptance determination system for a fixed length cell handling exchange as claimed in claim 23, wherein a use requested band requested to set from one of said second terminals is added as band information to a frame call from the second terminal and then transferred to said virtual band calculation means of said common resource call acceptance determination means together with the frame call.

30. A call acceptance determination system for a fixed length cell handling exchange as claimed in claim 15, wherein said common resource call acceptance determination means includes:

common resource fixed length cell call acceptance determination means for determining whether or not a fixed length cell call from one of said first terminals should be accepted when the first terminal tries to use the network common resource; and

common resource frame call acceptance determination means for determining whether or not a frame call from one of said second terminals should be accepted when the second terminal tries to use the network common resource.

31. A call acceptance determination system for a fixed length cell handling exchange as claimed in claim 30, wherein said common resource frame call acceptance determination means includes:

virtual band setting means for setting, when setting of a frame call is requested from one of said second terminals, a physical maximum speed of the second terminal as a use virtual band for the frame call;

band assurance determination means for determining whether or not a band has been assured already for a same sending subscriber as the second terminal on the network common resource;

common resource free band detection means for detecting a free band on the network common resource of said exchange;

comparison means for comparing the use virtual band set by said virtual band setting means and the free band detected by said common resource free band detection means with each other; and

call acceptance means for accepting, when said band assurance determination means determines that a band has been assured already for the same sending subscriber as the second terminal, the frame call from the second terminal unconditionally and for assuring, when said band assurance determination means determines that no band has been assured as yet for the same sending subscriber as the second terminal and the comparison by said comparison means proves that the use virtual band is smaller than the free band on the network common resource, the use virtual band and accepting the frame call from the second terminal.

32. A call acceptance determination system for a fixed length cell handling exchange as claimed in claim 30, wherein said common resource frame call acceptance determination means includes:

virtual band setting means for setting a use requested band requested to set for a frame call from one of said second terminals as a use virtual band for the frame call;

band assurance determination means for determining whether or not a band has been assured already for a same sending subscriber as the second terminal on the network common resource;

common resource free band detection means for detecting a free band on the network common resource of said exchange;

first comparison means for comparing, when said band assurance determination means determines that no band has been assured as yet for the same sending subscriber as the second terminal, the use virtual band set by said virtual band setting means and the free band detected by said common resource free band detection means with each other;

assured band extraction means for extracting, when said band assurance determination means determines that a band has been assured for the same sending subscriber as the second terminal, the band assured already for the second terminal;

second comparison means for comparing the band extracted by said assured band extraction means and a physical maximum speed of the second terminal with each other;

third comparison means for comparing, when the comparison by said second comparison means proves that the band extracted by said assured band extraction means is equal to or lower than the physical maximum speed of the second terminal, a sum of the band extracted by said assured band extraction means and the use virtual band set by said virtual band setting means and the physical maximum speed of the second terminal with each other;

remaining available band calculation means for subtracting, when the comparison by said third comparison means proves that the sum is higher than the physical maximum speed of the second terminal, the band extracted by said assured band extraction means from the physical maximum speed of the second terminal to calculate a remaining available band;

fourth comparison means for comparing the remaining available band calculated by said remaining available band calculation means and the free band detected by said common resource free band detection means with each other;

fifth comparison means for comparing, when the comparison by said third comparison means proves that the sum is equal to or lower than the physical maximum speed of the second terminal, the use virtual band set by said virtual band setting means and the free band detected by said common resource free band detection means with each other; and

call acceptance means for assuring, when the comparison by said first comparison means or said fifth comparison means proves that the use virtual band is smaller than the free band on the common resource, the use virtual band and accepting the frame call from the second terminal, for assuring, when the comparison by said fourth comparison means proves that the remaining available band is smaller than the free band on the common resource, the remaining available band and accepting the frame call from the second terminal, and for accepting, when the comparison by said second comparison means proves that the band extracted by said assured band extraction means is higher than the physical maximum speed of the second terminal, the frame call from the second terminal unconditionally.

33. A call acceptance determination system for a fixed length cell handling exchange as claimed in claim 32, wherein, for each of said second terminals connected to said exchange by way of said respective subscriber lines, a use band table is provided for controlling and storing a physical maximum speed of the second terminal and a sum total of use requested bands which have been requested to set before the present point of time by the second terminal, and said assured band extraction means extracts the sum total of the use requested bands of the use band table as a band assured already for the second terminal whereas the physical maximum speed of the second terminal which is to be used by said second comparison means, said third comparison means and said remaining available band calculation means is read out from the use band table.

34. A call acceptance determination system for a fixed length cell handling exchange as claimed in claim 32, wherein a use requested band requested to set from one of said second terminals is added as band information to a frame call from the second terminal and then transferred to said virtual band setting means of said common resource frame call acceptance determination means together with the frame call.

35. A call acceptance determination system for a fixed length cell handling exchange as claimed in claim 33, wherein a use requested band requested to set from one of said second terminals is added as band information to a frame call from the second terminal and then transferred to said virtual band setting means of said common resource frame call acceptance determination means together with the frame call.

36. A variable length frame exchanging interface apparatus which is interposed in a transmission line having at least one channel for interconnecting an exchange which handles fixed length cells each including a first logic channel information, a logic path information and a data section and a terminal adapted for a data communication using a variable length frame including a second logic channel information and which performs conversion processing between the fixed length cells for said exchange and a variable length frame for said terminal, the apparatus comprising:

frame disassembling means for disassembling the variable length frame transmitted from said terminal into fixed length cells;

translation means for translating the second logic channel information in the variable length frame into the first logic channel information and the logic path information for the fixed length cells; and

means for providing the first logic channel information, and the logic path information obtained in said translation means for the fixed length cells obtained in said frame disassembling means and inputting the fixed length cells with the first logic channel information and the logic path information to said exchange.

37. A variable length frame exchanging interface apparatus which is interposed in a transmission line having at least one channel for interconnecting an exchange which handles fixed length cells each including a first logic channel information, a logic path information and a data section and a terminal adapted for a data communication using a variable length frame including a second logic channel information and which performs conversion processing between the fixed length cells for said exchange and a variable length frame for said terminal, the apparatus comprising:

means for producing, when fixed length cells designating said terminal as a destination of transmission are outputted from said exchange to said transmission line, a frame from the fixed length cells;

translation means for translating the first logic channel information and the logic path information for the fixed length cells into the second logic channel information in the variable length frame; and

means for providing said frame obtained in said producing means with the second logic information obtained in said conversion means and inputting said frame with the second logic channel information in the variable length frame obtained in said translation means to said terminal.

38. A variable length frame exchanging interface apparatus which is interposed in a transmission line having at least one channel for interconnecting an exchange which handles fixed length cells each including a first logic channel information and a data section and a terminal adapted for a data communication using a variable length frame including a second logic channel information and which performs conversion processing between the fixed length cells for said exchange and a variable length frame for said terminal, the apparatus comprising:

frame disassembling means for disassembling the variable length frame transmitted from said terminal into fixed length cells;

first conversion means for converting the second logic channel information in the variable length frame into the first logic channel information for the fixed length cells;

first means for providing the first logic channel information obtained in said first conversion means for the fixed length cells obtained in said frame disassembling means and inputting the fixed length cells with the first logic channel information to said exchange;

means for producing, when fixed length cells designating said terminal as a destination of transmission are outputted from said exchange to said transmission line a frame from the fixed length cells;

second conversion means for converting the first logic channel information for the fixed length cells into the second logic channel information in the variable length frame; and

second means for providing said frame obtained in said producing means with the second logic channel information obtained in said second conversion means and inputting said frame with the second logic channel information in the variable length frame obtained in said second conversion means to said terminal.